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PHYSIO  January 2001

PHYSIO January 2001

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Subject:

Re: Correct Muscle Action? (fwd)

From:

Robert Treharne Jones <[log in to unmask]>

Reply-To:

PHYSIO - for physiotherapists in education and practice <[log in to unmask]>

Date:

Fri, 12 Jan 2001 05:10:36 -0000

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (127 lines)

Dear Glenn

Your settings may not be correct in the JISCMAIL websie if you are not
receiving copies of your own mailings.
Have a look at www.jiscmail.ac.uk

Robert

----- Original Message -----
From: "glenn alan welke" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, January 12, 2001 02:24
Subject: Re: Correct Muscle Action? (fwd)


> Hello,
> I sent this message out to the list a few days ago but am not real sure it
> went anywhere as I did not get a copy in my box.  Sorry to bother with a
> double post if that is what this is.
> Glenn
>
> ---------- Forwarded message ----------
> Date: Wed, 10 Jan 2001 08:27:33 -0500 (EST)
> From: glenn alan welke <[log in to unmask]>
> To: PHYSIO - for physiotherapists in education and practice
>     <[log in to unmask]>
> Subject: Re: Correct Muscle Action?
>
> Hello,
> I am a physical therapist with not much training in formal biomechanics
> or EMG stuff.  In reading this post aabout correct muscle action it seems
> that it indicates that there is an improvement in the "core stability" of
> the lifters within their training session.  Does not the decrease in
> external sway... indicate an increase in the central postural control/
> proprioceptive response system?  Would'nt the variation in the EMG
> activity of the trained lifters indicate the rapidly changing muscle
> activity that would be required to maintain a more precise trajectory?  If
> my thinking is along the correct lines I do not see why this is the
> opposite of what would be expected if the "correct muscle recruitment"
> hypothesis were to be believed.  Does this mean that if the correct muscle
> recruitment hypothesis was correct that there would be less EMG activity
> as well as less sway/smoother trajectory of the lift?  My understanding of
> core stability is that it is a pattern of muscle recruitment that improves
> stability centrally that allows a more precise movement distally.  It is
> not meant to produce a rigidity which would seem to make precision more
> difficult.  Trunk stability is a concept that therapist that work with the
> neurologically involved population have used for years on an intuitive
> basis I guess.
> Thanks for reading this jumbled message,
> Glenn
>
>
> On Fri, 5 Jan 2001 [log in to unmask] wrote:
>
> > Currently there is a great deal of discussion of the "correct" posture
and
> > pattern of moving or lifting, but there are at least two processes
involved:
> >
> > 1.  The 'correctness', precision, repeatability of the external movement
of
> > the body
> > 2.  The 'correctness', precision, repeatability of the internal muscle
> > involvement
> >
> > Most of the discussion of core stabilisation, transversus abdominis
> > recruitment and rotator cuff action suggests that both of the above
processes
> > take place in a very deterministic manner.  Thus, it is implied that the
> > pattern of external posture or movement is "correct" if the pattern of
> > internal muscle involvement is "correct".   Moreover, this also implies
that
> > the same pattern of muscle action always produces the same output motor
> > pattern and any other pattern of muscle action cannot do so.
> >
> > This functional relationship, however, has not been confirmed to be
correct,
> > yet it is assumed so often that many folk seem to accept that it is
virtually
> > a law.  Several studies involving simultaneous video recording of the
> > external movement and EMGs of given muscles has shown that this
assumption is
> > far form the truth.
> >
> > For example, the Russian scientist Pakhamov analysed the variation in
muscle
> > EMGs during the Olympic lifts and found that the least variation took
place
> > in the external movement, but there was significant variation in the EMG
> > indicators (Zhekov IP "'Biomechanics of the Weightlifting Exercises',
1976).
> >  Interestingly, the variation of all the functional indicators decreases
with
> > increase in load on the bar, but was much wider with light loads or no
loads
> > at all.
> >
> > During a prolonged training session, the degree of variation changed.
With
> > novices and lower qualified lifters, the variation decreased during the
> > middle of the session, but rose towards the end.  In highly qualified
> > lifters, it was very interesting to discover that, as the variation in
the
> > trajectory of the bar decreased, the variation in EMG increased, which
is
> > precisely the opposite of what would be expected if the ideas of the
"correct
> > muscle recruitment" hypothesis are to be believed.
> >
> > As Zhekov noted, this corroborates Bernstein's hypothesis that, in the
> > repeated reproduction of a movement, one observes a "repetition without
> > repetition".  Apparently, the variation is a general characteristic of
> > programmed movement which allows one to create and store different motor
> > programs and to select the optimal movement variant in a given
situation.
> > This variational principle, according to Pakhomov,  provides a large
> > reliability to enable the athlete to produce the required movement.
> > Furthermore, this switching between controlling and muscle groups serves
to
> > delay the onset of fatigue and minimises any increase in injury risk.
> >
> > Dr Mel C Siff
> > Denver, USA
> > [log in to unmask]
> >
>

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